During the setup process, while connecting to the range extender for the first time, a user is required to type in the default Wireless credentials on the required field. You can find the default wireless settings on the back of your device on its product label. Once you are connected to the Wi-fi of the range extender, open a browser and you will be automatically redirected to the configuration page of the Linksys extender. If you are not automatically redirected, type extender.linksys.com on the address bar and hit enter.
https://linksys-extendersetup.net